With Canadians being confronted with a string of bitterly cold, winter weather, many people may be wondering what happened to global warming.

"Global warming is a slow but consistent increase in recorded global temperatures over the past 100 to 150 years," explained Brian Luckman, geography professor at Western. He said many factors affect the Earth's climate, including the sun's energy output, ocean circulation and volcanic eruptions.

"Greenhouse gases are also a factor," Luckman said, adding gases such as carbon dioxide and methane allow the sun's rays to enter our atmosphere, but block them from escaping when they are reflected off the Earth's surface. This process causes an overall gradual heating of the planet, he explained.

Then why does this winter feel so cold? "Global climate change isn't going to mean we don't have winters," said James Voogt, a Western geography professor. "We're always going to have variability in temperature," he said, noting that, when compared to temperatures in the past 50 years, this year is no colder than average  it just feels that way.

In fact, according to Luckman, the worldwide average temperature has risen a whopping 0.6 degrees Celsius over the past 50 years.

"That may not seem like much, but a drop of only five degrees would mean the difference between our climate now and 3,000 feet of ice over Toronto," Luckman said, while noting an increase in only two or three degrees could cause sea levels to rise significantly.

"In the past 30 to 40 years, most [global] warming has been due to human activities," said Colin Baird, a Western chemistry professor. He said a small minority of scientists do not think that human-related greenhouse gas emissions are the cause of the problem, however, the majority of experts still do.

"Human impacts are having a discernible effect," Voogt said, adding that, while the Earth has experienced fluctuations in greenhouse gases naturally, human emissions of carbon dioxide and methane have increased the current rate of heating to new levels.